When designing an electronic circuit, it is typical to use a circuit simulator such as SPICE or the like to reduce trial and error in designing. As recent electronic circuits operate at higher frequency and faster digitization rate, more precise processing is in need for the circuit simulator. In particular, for an electronic circuit with a capacitor, a result predicted by the circuit simulator often largely deviates from an expected result of actual circuit. Thus, higher accuracy is required for the circuit simulator to work with such an electronic circuit.
For example, as a technology that allows performing a highly accurate circuit simulation, Japanese Unexamined Patent Application Publication No. 2002-259482 (patent document 1) discloses an equivalent circuit model derivation method.
In this equivalent circuit model derivation method, given frequency characteristics of a capacitor are entered in the first step. In the second step, an equivalent circuit model representing either an RC circuit and an RL circuit or an RCL circuit is formed using a resistance (R), a capacitor (C), and an inductor (L) that are frequency independent. Subsequently, in the third step, an evaluation function is composed to evaluate the equivalent circuit model formed in the second step. In the fourth step, circuit constants are determined by minimizing the evaluation function composed in the third step.
With such a technology, the equivalent circuit model of either an RC circuit and an RL circuit or an RCL circuit is formed. By increasing the number of devices in the equivalent circuit model, the circuit simulator may be able to simulate accurately from a low frequency (a frequency lower than a self-resonant frequency of a modeling target device) to a high frequency (a frequency higher than the self-resonant frequency of a modeling target device).